1. Field of the Invention
The invention is directed to an improved valve for controlling fluids.
2. Description of the Prior Art
Valves for controlling fluids of the type with which this invention is concerned are known in the industry and are used for instance in a fuel injection valve, in particular a common rail injector, of an internal combustion engine of a motor vehicle.
One such valve is described for instance in European Patent Disclosure EP 0 477 400 A1. For actuation, this valve has a piezoelectric actuator. For transmitting the deflection of the actuator to a valve closing member, the valve has a hydraulic chamber, which functions as a hydraulic booster or coupling and tolerance compensating element. The hydraulic chamber, between two pistons defining it, of which one piston has a smaller diameter and is connected to the valve closing member to be triggered and the other piston has a larger diameter and is connected to the piezoelectric actuator, encloses a common compensation volume. The smaller-diameter piston or so-called actuating piston executes a stroke that is increased by the boosting ratio of the piston diameters, when the larger-diameter piston, the so-called displacement piston, undergoes a certain deflection by means of the piezoelectric actuator. Moreover, via a compensation volume, the hydraulic chamber can compensate for tolerances resulting from temperature gradients or different coefficients of temperature expansion in the materials used as well as possible settling effects, without causing a change in the position of the valve closing member to be triggered.
The fluid pressure in the hydraulic coupler always drops upon actuation of the valve, because of leakage. For this reason, it is necessary that the hydraulic coupler be constantly replenished with suitable quantities of hydraulic fluid. In an injection valve, filling the coupler is done as a rule with fluid which is delivered to the injection valve at high pressure and which on the one hand represents the fluid to be injected by the injection valve into the engine and on the other is used to control the injection valve. Tapping the fluid is done via a leakage point, which for the sake of avoiding high pressure in the coupler has a small hydraulic cross section, for instance, or in other words a throttle restriction.
It proves problematic, however, that a throttle restriction of this kind can easily become plugged because of contaminants in the fluid flowing through it.
The valve of the invention in which the valve closing member has a pistonlike cylindrical region that together with the valve body forms at least one filter gap for fluid to be delivered to the filling device and at whose height an inlet conduit of the filling device branches off, has the advantage over the prior art that the risk of plugging up of a throttle restriction of the filling device, such as a throttle pin or throttle bore, is low, since the valve closing member in combination with the valve body forms a dirt filter for the fluid for filling the hydraulic coupler that flows through the throttle restriction.
The valve of the invention furthermore has the advantage that the dirt filter, formed of the valve body and the valve closing member, is a more or less self-cleaning dirt filter, since contaminants which may adhere in the region of the filter gap come loose again as a result of the motion of the valve closing member.
The invention is easy to realize by providing that the filter gap is achieved by guiding the pistonlike valve closing member closely on the valve body, for instance in an essentially correspondingly embodied bore therein. It is naturally important here that the inlet conduit branch off downstream from at least one filter gap. Otherwise, adequate filtering action could not be achieved.
In a preferred embodiment of the valve of the invention, the pistonlike region of the valve closing member is embodied on at least one annular protrusion of the valve body, which protrusion, embracing the valve closing member, together with the pistonlike region of the valve closing member forms the filter gap.
In an advantageous embodiment, the inlet conduit of the filling device can branch off from an annular chamber surrounding the pistonlike region of the valve closing member. This annular chamber is then expediently located downstream of the filter gap.
To enable furnishing the valve with a sufficient control quantity of fluid, the valve preferably has a control conduit, which establishes a communication between a chamber, embodied on the side of the valve closing member remote from the actuating piston, and the control chamber. The control chamber is disposed for instance such that it surrounds the region of the valve closing member that also includes the region of the valve closing member that cooperates with the valve seat.
Advantageously, a throttle can be embodied in the control conduit. If the valve of the invention is used in a common rail injector, in which the valve serves to control a so-called nozzle module and is connected to the nozzle module via a so-called outlet throttle, this throttle should have a larger cross section than the outlet throttle preceding it. Because of the throttle disposed in the control conduit, forces then ensue at the valve closing member that bring about fast closure of the valve closing member. This in turn, in an injection valve, assures small, stable injection quantities.
The control conduit can be embodied either in the valve closing member or in the valve body, depending on the preference of one skilled in the art.
In a special embodiment of the valve of the invention, the valve closing member is embodied in at least two parts. For instance, the valve closing member includes at least one substantially hemispherically shaped component, which cooperates with the valve seat, and one substantially cylindrically embodied component, which is guided on the valve body and with it forms the filter gap. This embodiment makes greater tolerances in producing the valve body possible, since when the hemispherically shaped component and the cylindrical region are embodied as displaceable radially relative to one another, the guide for the cylindrical region need not be embodied concentrically with the valve seat.
Adjusting a stroke of the valve closing member that occurs upon actuation of the actuating piston can be done by means of a stroke adjusting element, which is preferably embodied in the form of a disk and is disposed on the free face end of the valve closing member.